Friday, September 29, 2023

Why exactly three meals a day?

From a historical and cultural point of view, the famous lunch-dinner-dinner sequence is not universal. For a long time, our hunter-gatherer ancestors did not have access to consistent food sources and had few means to preserve what they found, so they ate when they could, and probably as much as they could. Proof of this is that the human body shows clear adaptations to making reserves: normally between 15 and 30% of our weight is made up of fat, while in our closest cousin, the chimpanzee, it is around 1%.

In ancient times, Romans only ate one real meal a day, in the late afternoon; They also had two light snacks in the morning and at noon. In the Middle Ages, many people ate twice a day, but eating habits varied greatly over time, and still today vary greatly from one country to another, we read in an article published on “The cultural aspects of meals and their frequency.” ” in the British Journal of Nutrition.

Now, if the Western habit of three meals a day is not universal, is it still preferable from a health point of view? Or would it be, on the contrary, harmful?

In fact, it is far from clear. As we can read in a review of the scientific literature published in 2019 in Nutrients, there were some studies that, starting in the 60s, observed that levels of fat and LDL (“bad cholesterol”) in the blood were higher in people. who ate only one or two large meals a day than those who ate smaller snacks, but more frequently: four or more times a day. A bit as if eating a lot at once favors the storage of reserves more than eating little by little, since the body needs it.

Many, many other works have subsequently examined the question of meal frequency, the effects of skipping lunch, etc. But the portrait that emerged is not particularly clear. For example, some studies have found that eating just one or two large meals a day is associated with a 26% increased risk of diabetes, and a 21% increase for those who skip lunch. But other research has not seen any notable effect on meal frequency. And others have concluded that, on the contrary, it is better to eat only one or two large meals a day.

It is not surprising, under these conditions, that experts do not always agree on how to interpret all these studies. In 2017, the American Heart Association published a “scientific advisory” in the medical journal Circulation warning of the clear risks of skipping breakfast. But many other researchers believe that the evidence on this topic is “equivocal” at best.

Regarding meal/snack frequency, an expert committee tasked with updating the US dietary guidelines concluded in 2020 that the available evidence was inconclusive.

Difficult tests to do.

In short, it is not at all obvious that eating three times a day is better (or worse) than having more (or fewer) meals/snacks. And this probably isn’t too surprising, because nutrition studies are notoriously difficult to do in “real life.” Eating habits are entangled with all sorts of variables that are often impossible to fully unravel; For example, the habit of skipping lunch is more common among certain disadvantaged and poorer groups, and since poverty is statistically associated with various health problems, it can create the illusion that skipping lunch is harmful.

Likewise, the number of meals is one thing, but the quality of what you eat each time is another. However, several of the studies cited above mention that people who skip lunch and/or eat fewer meals per day have, on average, a poorer quality diet. Researchers have mathematical tools to neutralize these “confounding factors,” as they are called, but it is often impossible to do so perfectly.

However, there are two things that seem to become increasingly clear in this area of ​​research. The first is that the time of eating matters. Human beings have internal “clocks” that stimulate activity during the day and slow it down at night. The main of these “clocks” is influenced by luminosity, but there are other “secondary clocks” that can be activated by eating. And if we eat a meal or a “snack” late at night, this can desynchronize our clocks, with harmful consequences for our health: obesity, diabetes, etc.

The second thing is that intermittent fasting seems to have beneficial effects, even when it only lasts about fifteen hours. All the works cited above, and others, go in this direction.

There are still gray areas and uncertainties, but a scientific consensus appears to be emerging in both cases, although the evidence has not yet been fully established.

Nation World News Desk
Nation World News Desk
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